This invention relates to classifying or sorting devices, and more particularly to a slat conveyor type sorting device in which an article sorting operation is carried out with a slat conveyor which is suitable for conveying articles different in configuration and in size.
There are available a variety of sorting devices in the art; for instance, a sorting device of the wheel float type, a sorting device of the push-out type, a sorting device of the tilt type, a sorting device using obliquely driven belts, and a sorting device using moving shoes on a slat conveyor. The slat conveyor is suitable for conveying articles different in configuration or in size. In the case of the slat conveyor, its sorting device employs moving shoes which are moved along the slats forming the conveying surface (i.e., in a direction perpendicular to the direction of conveyance of the conveyor).
Such a sorting device has been disclosed, for instance, by Japanese Patent Application Publication No. 10971/1985 or U.S. Pat. No. 4,738,347. The fundamental arrangement of the sorting device incorporated in the slat conveyor is as follows: Each slat has a moving shoe which is slidable longitudinally. The moving shoe is designed as shown in FIG. 22. That is, a projected member 8 extended downwardly from each of the slats (which may be a pin extended downwardly therefrom or a member having a roller) is guided by a main rail 10 or a branch rail 11 of a guide rail 9 installed below the slats. The projected member 8 is moved longitudinally of the slat being guided by the branch rail 11 which is extended obliquely on one side of the conveyor. A conveying-direction change-over device is provided at a predetermined sorting position, and its change-over member, namely, a change-over lever 22 is swung clockwise (in the direction of the arrow C) about a fulcrum 23, as a result of which the projected member moving in a predetermined direction (in the direction of the arrow) is caused to move towards the branch rail 11. In this operation, an article which has reached the sorting position is moved laterally of the conveyor (i.e., in the direction of the branch rail) by the shoe, thus being classified or sorted.
In addition, a sorting device with moving shoes, which has a conveying direction change-over mechanism utilizing a magnetic attraction force, is known in the art. Such a change-over mechanism disclosed, for instance, by Japanese Patent Application Publication No. 12982/1977 is as shown in FIG. 23. That is, permanent magnets 25 are fixedly secured to slide members 24, respectively. Electromagnets 27 arranged at the introducing end and conveying path change-over position of a magnetic guide 26 are so energized as to be equal in polarity to the permanent magnets 25, so that the slide members 24 with the magnetic elements are spaced from the magnetic guide 26 by the force of repulsion, thereby to form an article conveying path, so that an article X is conveyed to the desired one of the branch conveying paths D, E and F.
As is apparent from the above description, in the conventional change-over mechanism with the change-over lever, it is necessary to increase the length of the change-over lever 22 in proportion to the diameter (d) of the projected member 8. In addition, when the opening angle .theta. between the main rail 10 and the branch rail 11 is increased, it is also necessary to increase the opening angle .alpha. of the change-over lever 22, because it must be substantially equal to the opening angle .theta.. When the length of the change-over lever 22 is increased as was described above, then the rotational moment of the change-over lever 22 is increased, and accordingly it is necessary to increase the force of driving the change-over lever 22 as much. In addition, if the opening angle .alpha. of the change-over lever 22 is increased, then the amount of swing of the lever 22 is increased. This means that it takes a relatively long time to accomplish the predetermined operation.
In a case where the conveyor driving speed is increased, this difficulty may be eliminated by increasing the speed of operation of a drive system for the change-over lever 22, such as an electromagnetic valve or an air cylinder. However, the method is disadvantageous in the following points: As the drive system is improved in performance, the sorting conveyor is increased in size, or in manufacturing cost. Furthermore, as the length of the change-over lever 22 is increased, the speed of movement of the change-over lever 22, particularly at its end, is increased in proportion to the speed of rotation, as a result of which the lever is greatly shocked when stopped. Hence, in addition to the change-over lever itself, the members around it must be mechanically reinforced.
Therefore, if, when it is intended to increase the speed of operation of the change-over lever 22, the opening angle .alpha. is decreased to reduce the period of time required for completion of the predetermined operation, then it is not suitable for the case where the projected member 8 is large in diameter and the angle .theta. of the branch rail 11 is large.
The mechanism which utilizes the magnetic force of attraction to change the conveying path, as disclosed by the aforementioned Japanese Patent Application Publication 12982/1977, is high in manufacturing cost, because the permanent magnet 25 must be coupled to each of the number of slide members 24 forming the conveying path.
The conveying path in the branching direction is formed by attracting the slide members having the permanent magnets towards the magnetic guide 26. Therefore, the magnetic guide 26 should be extended over the entire length of the conveying path in the branching direction, which increases the manufacturing cost as much.
Furthermore, since the conveying path in the branching direction is formed by attracting the slide members towards the magnetic guide 26 as was described above, when it is required to perform a high speed conveyance by moving the slide members 24 at high speed, or when the article X on the slide members 24 is heavy, it is necessary to increase the magnetic force of attraction between the permanent magnets of the slide members and the magnetic guide accordingly. For this purpose, magnets or magnetic substances high in magnetic characteristic must be used, which also increases the manufacturing cost.
On the other hand, in the case where the slide members and the magnetic guide are high in magnetic characteristic, the electromagnets must be accordingly high in magnetic performance which are adapted to produce a force of repulsion to space the slide members from the magnetic guide in changing the conveying path. Accordingly, the electromagnets employed are unavoidably bulky.
Also, the conventional slat conveyor type sorting device using a moving shoe and a projected member is provided with a cross section portion where two guide rails forming respective guide paths cross each other in order to allow the moving shoe or projected member to go obliquely over the entire width of the conveying surface rightward or leftward selectively.
Japanese Patent Application Publication No. 11488/1984 discloses a change-over member used in such cross-section portion as shown in FIG. 26. Pawl-shaped end parts 39a and 39b are pivotally coupled to the end portions (closer to the intersection) of the upstream parts of the guide rails 34a and 34b, respectively. A selected one of the right and left end parts 39a and 39b is swung about the respective fulcrum 40, to switch the conveying paths extended to the downstream parts of the guide rails.
In addition, a change-over mechanism as shown in FIGS. 24 and 25 has also been disclosed by the aforementioned Japanese Patent application Publication No. 11488/1984. In the mechanism, each projected member 32 is made up of a throttle epicyclic wheel 41, and a pair of rollers 42 arranged on both side of the epicyclic wheel 41. The projected member 32, being guided by movable boards 43 arranged on the rear side of the conveying surface along both right and left edges, is moved along guide rails 34 in the direction of the arrow which are arranged as shown in FIGS. 24 and 25. Each of the guide rails is partially omitted a length shorter than the distance between the two rollers 42 but larger than the diameter of the epicyclic wheel 41; that is, it has a space 38 corresponding to the length. Therefore, the projected member 32 is moved to the following (downstream) guide rail 34 while passing through the space 38.
However, the above-described change-over mechanism suffers from various disadvantages.
That is, in the mechanism, as shown typically in FIG. 26, the change-over members 39a and 39b are arranged in the cross section portion, so that the guide rails are switched mechanically so as to allow the projected member to move to the following guide rail. Therefore, it is necessary to operate the change-over member 39 whenever it is required to switch the conveying paths. Hence, the mechanism is relatively low in durability, and produces noises whenever operated, thus adversely affecting the working environment.
The change-over member 39 is made up of a pair of end parts 39a and 39b as was described above. Hence, in switching the guide rails, it is essential to control the timing of operating (swinging) the end parts 39a and 39b with high accuracy. Accordingly, the mechanism is unavoidably intricate in arrangement. In particular, in order to switch the guide rails at high speed, it is necessary to increase the mechanical strength of the drive system of the change-over member 39, and to operate the control system with higher accuracy. This means an increase in manufacturing cost or in running cost.
In addition, it is necessary to provide the change-over member 39 at each of the guide rail cross sections, and therefore, the resultant sorting device is increased in manufacturing cost as much.
On the other hand, the change-over mechanism as shown in FIGS. 24 and 25, having no mechanical change-over member as shown in FIG. 26, is free from the above-described difficulties that it is low in durability, produces noises, or it is high in manufacturing cost or running cost. However, it is still disadvantageous in the following point: That is, if the space 38 is not accurately aligned with the adjacent guide rails, then the front end of the projected member collides with the junction 44 of the guide rails, so that the projected member is not smoothly moved over to the following guide rail, which may result in the occurrence of a trouble with the sorting device. This is a serious problem particularly when the conveying speed is high.
Accordingly, an object of this invention is to eliminate the above-described difficulties accompanying a conventional sorting device. More specifically, an object of the invention is to provide a sorting device which is able to classify or sort articles on the conveying surface accurately and quickly, and which produces no noises in changing the conveying path, and in which the change-over mechanism is simple in arrangement and low in manufacturing cost. Another object of this invention is to provide a sorting conveyor change-over device which is low in manufacturing cost and simple in arrangement, and which is suitable for a high speed conveying operation, thus permitting articles to be classified or sorted positively and quickly.